Conventionally, as a technique to improve safety of a vehicle such as a four-wheeled vehicle, a technique to avoid collision by determining risk that the vehicle collides with the obstacle with high accuracy is known. For example, the following patent document 1 discloses the technique relating to a collision avoidance apparatus provided with a yaw rate sensor for detecting yaw rate of a subject vehicle, a velocity detection device for detecting a velocity of the subject vehicle, and a radar device for detecting a position and a velocity of a surrounding obstacle.
In the conventional technique, a predicted travel trajectory of the subject vehicle is obtained by the yaw rate sensor and the velocity sensor and a predetermined area on both sides of the predicted travel trajectory is obtained as a predicted travel area of the subject vehicle, and on the other hand, a predicted travel trajectory and a predicted travel area of the obstacle are obtained based on a position and a velocity of the obstacle detected by the radar device. After that, a collision point or an adjacent point of the both is calculated from each predicted travel area of the subject vehicle and the obstacle. Also, collision risk is determined by calculating target deceleration and acceleration and target deceleration, and when the risk of collision arises as a result of the determination, a velocity control of the subject vehicle is performed according to the target deceleration and acceleration and the target deceleration.
Patent Document 1: Japanese Patent No. 2799375